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NASA is testing technologies in space and on Earth that can increase bandwidth to transmit more complex scientific data and even broadcast video images from Mars. NASA’s Deep Space Optical Communications (DSOC) project, which begins this fall, is testing how lasers can accelerate data transmission beyond the capability of current radio-frequency systems used in space. Better known as a technology showcase, DSOC could pave the way for the broadband communications that will power humanity’s next giant leap: when NASA sends astronauts to Mars.
The DSOC (Device that can transmit and receive data) near-infrared laser transceiver on NASA’s Psyche mission will travel when it blasts off to the mineral-rich asteroid of the same name in October. For the first two years of the flight, the transponder will communicate with two ground stations in Southern California, where highly sensitive detectors, powerful laser transmitters and new methods for decoding signals from deep space will be tested.
NASA is focusing on laser or optical communications because they can exceed the bandwidth of radio waves, which is what the space agency has relied on for more than half a century. Both laser and near-infrared radio communications use electromagnetic waves to transmit data, but near-infrared light packs data into tighter wavelengths, allowing ground stations to receive more data at one time.
“DSOC is designed to demonstrate the data return capability of up to 10 to 100 times that of modern radio systems currently deployed in space,” said Abi Biswas, DSOC project technology expert at NASA’s Jet Propulsion Laboratory in Southern California. “High-bandwidth laser communication has been demonstrated to satellites orbiting the Earth and the Moon, but deep space presents us with new challenges.”
More missions are on the way to deep space than ever before, and they promise to produce exponentially more data than previous missions in the form of sophisticated science measurements, high-definition images and videos. Thus, experiments like DSOC will play a critical role in helping NASA develop technologies that can be used routinely by spacecraft and ground systems in the future. “DSOC represents the next phase in NASA’s plans to develop revolutionary enhanced communications technologies that have the potential to augment data transmission from space — critical to the agency’s future aspirations,” said Trudy Curtis, technology program manager. TDM) at NASA Headquarters in Washington. “We are thrilled to have the opportunity to test this technology during Psyche’s flight.”
The DSOC instrument aboard the Psyche spacecraft – Image: NASA/JPL
Pioneering technologies
The transceiver on Psyche is equipped with several new technologies, including a never-before-launched photon camera connected to a 22-centimeter aperture telescope protruding from the side of the spacecraft. The transceiver will independently scan and mount on a high-energy near-infrared laser uplink emitted by the Optical Communications Telescope Laboratory at JPL’s Table Mountain facility near Wrightwood, California. The laser uplink will also indicate the transmission of commands to the transceiver.
“The high-energy uplink laser is a critical part of this technology demonstration of faster spacecraft speeds, and upgrades to our ground-based systems will enable optical communications for future deep-space missions,” said Jason Mitchell, NASA Astronautics and Communications Program Manager. (SCaN) at NASA Headquarters.
Once locked onto the uplink laser, the transceiver will locate the 200-inch (5.1-meter) Hale telescope at Caltech’s Palomar Observatory in San Diego County, California, about 80 miles south of Table Mountain. The transceiver will then use a near-infrared laser to transmit high-speed data to Palomar. Vibrations from the spacecraft that could throw the laser off its target are damped by advanced mounts that secure the transponder to Psyche.
For fast downlink laser reception from the DSOC transceiver, the Hale telescope was equipped with a new superconducting nanowire photon detector. The array is cryogenically cooled so that a single laser photon (a quantum particle of light) can be detected and its arrival time recorded. The laser light is sent out as a series of pulses and must travel more than 300 million kilometers – the farthest a spacecraft will travel during this geometry – before the weak signals can be detected and processed to extract information from them.
“Every part of DSOC features new technology, from the powerful uplink lasers to the aiming system on the transceiver telescope and the highly sensitive detectors that can count individual photons as they arrive,” said Bill Klebstein, DSOC project manager at JPL. “The team even had to develop new signal processing techniques to extract information from these weak signals that travel over huge distances.”
Distances present another challenge to the technology display: the farther Psyche travels, the longer it takes photons to reach their destination, causing delays of up to tens of minutes. The positions of the Earth and spaceship are constantly changing as the laser photons travel, so this delay must be compensated for. “Guiding and stabilizing the laser over millions of miles while dealing with the relative motion of Earth and self is an exciting challenge for our project,” said Biswas.
source: NASA
